I don't need a unique widget for the whole website. I need N Facebook PagePlugin widgets to display within M nodes of a specific content type.

Setting up Facebook Page Plugin for every node on Drupal 7

# First, I've created a new text field for the content type called facebook_direction.
# Second, I got the facebook script given by Facebook Developers.
# Third, I wrote some PHP code for get the info about the current node and 
# processing the field values asociated to the node.
# Fourth, I've changed the URL values from the snippet with PHP code to get
# every facebook page from every node.
# Fifth, I made a new custom block in my Drupal site, called "facebook stream widget"
# Sixth, I've inserted the code in the custom block body with PHP editor active, 
# marking the block as only for content types of kind "companies".
# Add: I made sure that only the Facebook widget view is created yes and only if the 
# node has completed its field facebook direction. Otherwise, the widget is not 
# generated, line-> if (!is_null($direction)), so it does not show it empty.

# Here is the code and works fine:

<div id="fb-root"></div>
<script>(function(d, s, id) {
  var js, fjs = d.getElementsByTagName(s)[0];
  if (d.getElementById(id)) return;
  js = d.createElement(s); js.id = id;
  js.src = "//connect.facebook.net/es_ES/sdk.js#xfbml=1&version=v2.10";
  fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));</script>

<?php

$field = 'field_facebook_direction';
$node = menu_get_object();
$items = field_get_items('node', $node, $field);
$direction = $items[0]['value'];
 if (!is_null($direction)) {
?>
<div class="fb-page" data-adapt-container-width="true" data-hide-
cover="false" data-href="<?php
 echo $direction;?>" data-show-facepile="false" data-small-
header="false" data-tabs="timeline">

<blockquote cite="<?php echo $direction;?>" class="fb-xfbml-parse-
ignore">
<a href="<?php echo $direction;?>">Facebook  Stream</a></blockquote>
</div>

<?php
}

?>